Technically, the rifle and the para use different recoil systems. The rifle's recoil system is in the stock and the paratrooper's recoil system is mounted in the special top cover. Now, you can use a rifle stock with a para recoil system, and it would be easier to just change the whole lower receiver assembly. But, you can only change the rifle into a para by changing to the para recoil system.

Originally Posted By Lon_Moer:Technically, the rifle and the para use different recoil systems. The rifle's recoil system is in the stock and the paratrooper's recoil system is mounted in the special top cover. Now, you can use a rifle stock with a para recoil system, and it would be easier to just change the whole lower receiver assembly. But, you can only change the rifle into a para by changing to the para recoil system.

Yep.

Easy to change from para to fixed (and just continue to use the para recoil system), more parts involved the other way around.